View source for Unicode input

{{Short description|Input characters using their Unicode code points}}
[[Image:KCharSelect Mathematical Operators.png|thumb|345px|The [[List of KDE applications#Utilities|KCharSelect]] character mapping tool shown displaying a subset of the [[Unicode Mathematical Operators]]|alt=]]
[[File:New Unicode logo.svg|thumb|right|150px|The Unicode logo]]

'''Unicode input''' is method to add a specific [[Universal Character Set characters|Unicode character]] to a [[computer file]]; it is a common way to input characters not directly supported by a physical [[Keyboard (computing)|keyboard]].  Characters can be entered either by selecting them from a display, by typing a certain sequence of keys on a physical keyboard, or by drawing the symbol by hand on [[touch-sensitive screen]]. In contrast to [[ASCII]]'s 96 element [[character set]] (which it contains), Unicode encodes hundreds of thousands of [[grapheme]]s (characters) from almost all of the world's written languages and many other signs and symbols.<ref>{{cite web|last=Lafontaine|first=Sylvain|title=Unicode vs ASCII difference and benefits|url=http://social.msdn.microsoft.com/Forums/sqlserver/en-US/918f7c8b-cc16-4c03-b4f9-f9b0660e0587/unicode-vs-ascii-difference-and-benefits?forum=transactsql|publisher=MSDN|access-date=28 February 2014| date=February 17, 2012}}</ref>{{better source needed|date=May 2020}}

A Unicode input system must provide for a large repertoire of characters, ideally all valid Unicode code points. This is different from a [[keyboard layout]] which defines keys and their combinations only for a limited number of characters appropriate for a certain [[locale (computer software)|locale]].

== Unicode numbers ==
Unicode characters are distinguished by [[code point]]s, which are [[Unicode#Upluslink|conventionally represented]] by "U+" followed by four, five or six [[hexadecimal digit]]s, for example U+00AE or U+1D310. Characters in the [[Basic Multilingual Plane]] (BMP), containing modern [[Writing system|scripts]]&nbsp;– including many Chinese and Japanese characters&nbsp;– and many symbols, have a 4-digit code. Historic scripts, but also many modern symbols and pictographs (such as [[emoticon]]s, [[emoji]]s, [[playing card]]s and many [[CJK characters]]) have 5-digit codes.

== Glyph availability <span class="anchor" id="Availability"></span>==
An application can display a character only if it can access a [[computer font]] which contains a [[glyph]] for that character.<ref name="mswin">Andrew Marcuse, [https://www.fileformat.info/tip/microsoft/enter_unicode.htm "How to enter Unicode characters in Microsoft Windows"]. Access date: September 13, 2012</ref> Fonts usually have incomplete Unicode coverage; most only contain the glyphs needed to support a few [[writing system]]s. However,  most modern browsers and other text-processing applications are able to display multilingual content because they perform [[font substitution]], automatically switching to a fallback font when necessary to display characters which are not supported in the current font. Which fonts are used for fallback and the thoroughness of Unicode coverage varies by software and operating system; some software will search for a suitable glyph in all of the installed fonts, others only search within certain fonts.

{{anchor|.notdef.}} If an application does not have access to a glyph for a required codepoint in the specified font,{{efn|or in fallback font(s), if any.}} the character should be shown as the font's {{code|.notdef}} glyph {{angbr|&#x10FFEE;}}<!--This is code point U+10FFEE which is in the a private-use range and thus unlikely to have a glyph assigned. Consequently it should display as a replacement. -->.<ref>{{cite web |title=Recommendations for OpenType Fonts |url=https://learn.microsoft.com/en-us/typography/opentype/spec/recom |publisher=Microsoft|quote=Glyph 0 must be assigned to a .notdef glyph. The .notdef glyph is very important for providing the user feedback that a glyph is not found in the font. This glyph should not be left without an outline as the user will only see what looks like a space if a glyph is missing and not be aware of the active font’s limitation.}}</ref> This often appears as an empty box, ☐ (nicknamed "[[Noto fonts#Etymology|tofu]]" based on the shape), a box with an X in it, ☒, a diamond with a question mark, �, or a box with a question mark in it, ⍰.

==Techniques==
{{main|input method}}
===Extended keyboard mapping===
{{further|QWERTY#Multilingual variants}}
Most operating systems support extended [[keyboard mapping]]{{snd}} the facility to increase the repertoire of characters available using techniques such as [[Alternate graphic]] ("AltGr") that gives a third and fourth meaning to every key; [[Compose key]] (sometimes called '''multi key'''), a key on a [[computer keyboard]] that indicates that the following (usually 2 or more) keystrokes trigger the insertion of an alternate character, typically a [[precomposed character]] or a symbol;<ref>{{cite web |url=http://fsymbols.com/keyboard/linux/compose/ |title=Linux Keyboard Text Symbols: Compose-Key Shortcuts |website=FSymbols |date=2013-07-24 |access-date=2015-07-07}}</ref> [[dead key]]s typically used to attach a specific [[diacritic]] to a base [[letter (alphabet)|letter]];<ref>{{cite web|url=http://www.merriam-webster.com/dictionary/dead%20key |title=Dead Key &#124; Definition of Dead Key by Merriam-Webster |publisher=Merriam-webster.com |access-date=2017-05-01}}</ref> or indeed combinations of these.

These techniques facilitate entry of character sets beyond the basic set provided as standard with the computer.

=== Selection from a screen ===
[[File:20170802073953!GNOME Character Map 3.18.2.png|thumb|300px|GNOME Character Map]]

Many systems provide a way to select Unicode characters visually. [[ISO/IEC 14755]] refers to this as a ''screen-selection entry method''.<ref>{{cite web|url=https://www.iso.org/standard/25491.html|title = ISO/IEC 14755:1997 Information technology -- Input methods to enter characters from the repertoire of ISO/IEC 10646 with a keyboard or other input device|publisher=ISO|access-date=2017-10-14}}</ref>

[[Microsoft Windows]] has provided a Unicode version of the [[Character Map (Windows)|Character Map]] program, appearing in the consumer edition since XP. This is limited to characters in the [[Basic Multilingual Plane]] (BMP). Characters are searchable by Unicode character name, and the table can be limited to a particular code block.<ref>{{Cite web|date=Jul 31, 2019|title=How to Use Special Characters in Windows Documents|url=https://support.microsoft.com/en-us/help/315684/how-to-use-special-characters-in-windows-documents|access-date=2020-10-17|website=support.microsoft.com}}</ref> Starting with Windows 10 Microsoft Windows also contains so called "emoji keyboard". It can be started by holding down the [[Windows key]] and hitting the period or semicolon key. The emoji keyboard allows entering of emojis as well as symbols.<ref>{{Cite web|date=Feb 5, 2018|title=Windows 10 Tip: Get started with the emoji keyboard shortcut|url=https://blogs.windows.com/windowsexperience/2018/02/05/windows-10-tip-get-started-emoji-keyboard-shortcut/|access-date=2024-06-04|website=blogs.windows.com}}</ref> 

More advanced third-party tools of the same type are also available (a notable [[freeware]] example is [[Andrew West (linguist)#BabelMap|BabelMap]], which supports all Unicode characters). On most [[Linux]] desktop environments, equivalent tools&nbsp;– such as [[gucharmap]] (GNOME) or [[List of KDE applications|kcharselect]] (KDE)&nbsp;– are available.<ref>{{cite web |last=Peck |first=Akkana |date=2009-11-25 |title=Mastering Characters Sets in Linux (Weird Characters, part 2) |url=http://www.linuxplanet.com/linuxplanet/tutorials/6912/1 |url-status=dead |archive-url=https://web.archive.org/web/20101126084750/http://linuxplanet.com/linuxplanet/print/6912/ |archive-date=2010-11-26 |access-date=2018-12-05 |work=[[LinuxPlanet]]}}</ref>

Generally these tools let the user "copy" the selected characters into the clipboard, and then paste them into the document, rather than pretending to directly type them.

It is often practical to just find the desired character on the web or in another document, and copy and paste it from there.

=== Decimal input (Alt codes) <span class="anchor" id="Decimal input"></span> ===
{{More citations|section|date=October 2024}}

Some programs running in [[Microsoft Windows]], including recent versions of [[Microsoft Word|Word]] and [[Windows Notepad|Notepad]], can produce characters from their Unicode code points expressed in decimal and entered on the [[numeric keypad]] with the {{keypress|[[Alt code|Alt]]}} key held down.<ref>{{Cite web |title=Insert ASCII or Unicode character codes in Word - Microsoft Support |url=https://support.microsoft.com/en-us/office/insert-ascii-or-unicode-character-codes-in-word-e97306f7-00c1-490d-9920-c924ca443f87 |access-date=2025-02-08 |website=support.microsoft.com}}</ref>  For example, the [[Euro sign]] {{char|€}} has 20AC as its hexadecimal code point,<ref>{{Cite web |title=Currency symbols |url=https://www.unicode.org/charts/nameslist/n_20A0.html |access-date=2025-02-08 |website=[[Unicode Consortium ]]}}</ref> which is 8364 in decimal, so {{keypress|Alt|8}}{{keypress|3|6|4|chain=}} will produce the symbol. 

Decimal code points in the range 160 –255 must be entered with a leading zero (so that the [[Windows code page]] is chosen) and furthermore the Windows code page [[CP1252]] must be used.{{efn|CP1252 is the default in North and South America including the Caribbean islands, Western Europe, Central and Southern Africa, Australia, New Zealand, and the (former) European colonies and possessions in [[Oceania]]}} For example, {{keypress|Alt|0}}{{keypress|2|4|7|chain=}} yields a {{char|÷}}, corresponding to its code point, but the character produced by {{keypress|Alt|2}}{{keypress|4|7|chain=}} depends on the {{Pslink|Windows_code_page|OEM code page}}, such as [[Code page 437]], and may yield a&nbsp;{{char|≈}}. Also {{keypress|Alt|0}}{{keypress|1|2|8|chain=}} through {{keypress|Alt|0}}{{keypress|1|5|9|chain=}} yield the characters assigned in rows 8 and 9 in the [[Windows-1252#Codepage layout|CP1252 layout]], rather than the [[C0 and C1 control codes#C1 controls|C1 control codes]] that are assigned to those numbers in Unicode.

In programs which were not designed to handle Alt codes over 255, the character retrieved usually corresponds to the [[modulo operation|remainder]] when the number is divided by 256.

The text editor [[Vim (text editor)|Vim]] allows characters to be specified by two-character mnemonics referred to as [[digraph (computing)|digraphs]].<ref>{{Cite web |title=ii.com: Vim, Unicode, and Digraphs |url=https://www.ii.com/vim-unicode-digraphs/ |access-date=2025-02-08 |website=www.ii.com}}</ref>  The installed set can be augmented by custom mnemonics defined for arbitrary code points, specified in decimal.  For example, as decimal 9881 is equal to hexadecimal 2699, {{Code|dig Gr 9881}} associates "Gr" with {{unichar|2699|GEAR}}.

See [[#HTML|below]] for use of decimal code points in HTML.

=== Hexadecimal input ===

Clause 5.1 of [[ISO/IEC 14755]] describes a ''Basic method'' whereby a ''beginning sequence'' is followed by the [[hexadecimal|hex number]] representation of the [[code point]] and the ''ending sequence''. Most modern systems have some method to emulate this, sometimes limited to four digits (thus only the [[Plane (Unicode)#Basic Multilingual Plane|Basic Multilingual Plane]]).

==== In Microsoft Windows ====

Hexadecimal Unicode input can be enabled by adding a string type (REG_SZ) value called <code>EnableHexNumpad</code> to the [[Windows Registry|registry]] key <code>HKEY_CURRENT_USER\Control&nbsp;Panel\Input&nbsp;Method</code> and assigning the value data <code>1</code> to it. Users will need to log off and back in after editing the registry for this input method to start working. (In versions earlier than [[Windows Vista]], users needed to reboot for it to start working.) Unicode characters can then be entered by holding down {{keypress|Alt}}, and typing {{keypress|+}} on the numeric keypad, followed by the hexadecimal code, and then releasing {{keypress|Alt}}.<ref name="mswin" /> This may not work for 5-digit hexadecimal codes like {{code|U+1F937}}. Some versions of Windows may require the digits 0-9 to be typed on the numeric keypad or require NumLock to be on.{{citation needed|date=December 2022}}

In some applications ([[Microsoft Word|Word]], [[Windows Notepad|Notepad]] and [[LibreOffice]] programs) {{keypress|Alt|X}} will replace the hexadecimal number to the left of the cursor with the matching Unicode character. Unless it is six hexadecimal digits long, the code must not be preceded by any digit or letters a–f as they may be treated as part of the code to be converted. For example, entering <code>af1</code> followed by {{keypress|Alt|X}} (or {{keypress|Alt|C}} if using a French version) will produce '૱' (U+0AF1), but entering <code>a0000f1</code> followed by {{keypress|Alt|X}} will produce 'añ' ('a' followed by character U+00F1).

This facility enables Unicode characters to be entered in other applications: one can create a desired character in Notepad, for example, and then [[Cut, copy, and paste|cut and paste]] it wherever desired.

==== In MacOS ====

Hex input of Unicode must be enabled. In Mac OS 8.5 and later, one can choose the ''Unicode Hex Input'' keyboard layout; in [[OS X Yosemite|OS X (10.10) Yosemite]], this can be added in Keyboard → Input Sources.

Holding down {{key press|option}}, one types the four-digit [[hexadecimal]] Unicode code point and the equivalent character appears; one can then release the {{key press|option}} key.<ref>[http://mac.sillydog.org/archives/001703.php Typing special and accented characters] {{Webarchive|url=https://web.archive.org/web/20080309212927/http://mac.sillydog.org/archives/001703.php |date=2008-03-09 }}</ref> Characters outside of the BMP (the Basic Multilingual Plane) exceed the four-digit limit of the Unicode hex input mechanism but can be entered by using [[UTF-16#Description|surrogate pairs]]: holding down the {{keypress|Option}} key while entering the first surrogate, the {{keypress|+}}, the second surrogate, then releasing the Option key.

==== In X11 (Linux and other Unix variants including ChromeOS) ====

In many applications one or both of the following methods work to directly input Unicode characters:
* Holding {{keypress|Ctrl|Shift}} and typing {{keypress|u}} followed by the hex digits, then releasing {{keypress|Ctrl|Shift}}.
* Entering {{keypress|Ctrl|Shift|u}}, releasing, then typing the hex digits and pressing {{keypress|Enter}} (or {{keypress|Space}} or even, on some systems, pressing and releasing {{keypress|Shift}} or {{keypress|Ctrl}}).<ref name=gpost>{{cite web|url= https://www.groovypost.com/howto/type-special-characters-chromebook-accents-symbols-em-dashes | title = Type Special Characters with a Chromebook (Accents, Symbols, Em Dashes) | author = Jack Busch | website= groovypost.com | date = April 20, 2018 | access-date= February 28, 2020}}</ref>

This is supported by GTK and Qt applications, and possibly others. In ChromeOS, this is an operating system function.<ref name=gpost />

=== In platform-independent applications ===
* In [[Emacs]], {{keypress|[[Control key|Ctrl]]|x}}{{keypress|8}}{{keypress|Return}} invokes the {{code|insert-char}} command, which accepts input either via hex code point or unicode char name.
* In [[LibreOffice]] 5.1 onwards, the {{keypress|Alt|X}} method described above for Windows works.<!-- https://gerrit.libreoffice.org/gitweb?p=core.git;a=commitdiff;h=ff3c4f4c704977b2eec1dba1238b422537e413f3 - not sure if this counts as a “reference” -->
* In [[Opera (browser)|Opera]] versions that use the [[Presto (browser engine)|Presto layout engine]]—i.e. up to and including version 12.xx—, entering the hexadecimal number of the desired symbol or character and then pressing {{keypress|Ctrl|Shift|x}} (alternative shortcut {{keypress|[[Meta key|Meta]]|Shift||x}} on [[macOS]]).
* In the [[Vim (text editor)|Vim editor]], in insert mode, the user first types {{keypress|Ctrl|V}} {{keypress|u}} (for codepoints up to 4 hex digits long; using {{keypress|Ctrl|V}} {{keypress|Shift|U}}  for longer), then types in the hexadecimal number of the symbol or character desired, and it will be converted into the symbol.  (On Microsoft Windows, {{keypress|Ctrl|Q}} may be required instead of {{keypress|Ctrl|V}}.<ref name="vim_w32">[https://vimhelp.org/gui_w32.txt.html#mswin.vim Vim documentation: gui_w32]</ref>)
* In [[AutoCAD]] {{code|\U+2C72}} or three shortcuts {{code|%%c}}, {{code|%%d}}, {{code|%%p}}.

=== HTML ===
{{main|Numeric character reference}}
In [[Unicode and HTML|HTML]] and [[XML]], character codes to be rendered as characters are prefixed by [[ampersand]] and [[number sign]] (&amp;#), and are followed by a semicolon (;). The code point can be either in [[decimal]] or in [[hexadecimal]]; in the latter case it is preceded by an "x". Leading zeros may be omitted. A number of characters may be represented by a [[Character entity reference|named entity]].

''Example:'' In HTML/XML, the [[copyright sign]] © (<code>U+00A9</code>) may be coded as:
* <code>&amp;#169;</code> (decimal code point)
* <code>&amp;#xa9;</code> (hexadecimal code point)
* <code>&amp;copy;</code> (entity name)

This works in many pieces of software that accept HTML markup, such as [[Mozilla Thunderbird|Thunderbird]] and Wikipedia editing.

== See also ==
* [[ASCII]]
* [[Digraphs and trigraphs (programming)]]

==Notes==
{{notelist}}

== References ==
{{reflist}}

{{Unicode navigation}}

[[Category:Unicode|Input]]
[[Category:Input methods]]